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H Keilacker

Publications and source records attributed to H Keilacker.

50 records · Page 3Linked to original sources
PubMed1984

Monoclonal antibodies to human insulin and their antigen binding behaviour.

Mouse monoclonal antibodies were raised against human insulin by somatic cell hybridization using the mouse myeloma line P3-X63-Ag8. Five cell lines were grown as ascites producing tumors. Insulin binding data were determined from six monoclonal antibodies by Scatchard analysis. Each anti-insulin hybridoma antibody gave a straight-line Scatchard plot confirming the homogeneity of their binding sites and their monoclonality. The equilibrium dissociation constants ranged from 2.20 X 10(-8) to 4.48 X 10(-10) mol/l. We could demonstrate positive as well as negative cooperativity of monoclonal insulin antibodies by performing insulin binding studies with defined mixtures of two different anti-insulin hybridoma antibodies.

Animals↗
PubMed1982

Insulin antibodies in juvenile diabetes mellitus. Correlations to diabetic stability, insulin requirement and duration of insulin treatment.

We investigated the plasma insulin binding patterns of 15 insulin-treated juvenile diabetics with a very low residual B-cell function. Determination of the insulin binding was performed after removal of therapeutic insulin. 125I-monoiodoinsulin was used and insulin binding was measured over a large range of insulin concentration. Insulin binding parameters were evaluated by Scatchard analysis of the binding data. Significantly elevated insulin binding was detected when the diabetic control was stable. These patients had a lower insulin requirement and low equilibrium dissociation constants of the high affinity antibodies. Furthermore, a strong negative correlation between the duration of insulin treatment and insulin binding could be demonstrated resulting from both decreasing antibody affinities and maximum binding capacities. We discuss the stabilizing effect of insulin antibodies on the metabolic character assuming that dissociating insulin-antibody complexes mimic a "basal insulin secretion" similar to pancreatic B-cells with residual functional capacity.

Adolescent↗
PubMed1980

Radioligand assays-methods and applications. IV. Uniform regression of hyperbolic and linear radioimmunoassay calibration curves.

In order to handle all types of radioimmunoassay (RIA) calibration curves obtained in our laboratory in the same way, we tried to find a non-linear expression for their regression which allows calibration curves with different degrees of curvature to be fitted. Considering the two boundary cases of the incubation protocol we derived a hyperbolic inverse regression function: x = a1y + a0 + a-1y-1, where x is the total concentration of antigen, ai are constants, and y is the specifically bound radioactivity. An RIA evaluation procedure based on this function is described providing a fitted inverse RIA calibration curve and some statistical quality parameters. The latter are of an order which is normal for RIA systems. There is an excellent agreement between fitted and experimentally obtained calibration curves having a different degree of curvature.

Humans↗
PubMed1980

[Radioligand assay: method and application. II. Effect of glucagon coupling on the production of glucagon antisera with suitable binding parameters for radioimmunoassay].

Glucagon antibodies were produced in rabbits using three immunogenic glucagon conjugates. Glucagon was coupled to bovine serum albumin by difluorodinitrobenzene (DFDNB), carbodiimide (ECDI) or glutardialdehyde. Rabbits immunized with glucagon conjugated to albumin using DFDNB produced sensitive antisera for radioimmunoassay quite specific for pancreatic glucagon. The affinity constant of the best antiserum was approximately 10(11) l/mol. Antisera raised against the two other glucagon-conjugates were significantly less affine. All of these antisera showed inverse binding curves of 126J-glucagon caused by positive cooperatively in dependence upon the antigen/antibody ratio. The race of rabbits used for immunization was without influence on the immune response.

Animals↗
PubMed1980

Delayed or biphasic glucose-induced insulin secretion of pancreatic islets isolated from spiny mice (Acomys cahirinus) : relation to age of animals.

The dynamics of insulin release from spiny mouse perifused pancreatic islets was investigated. In agreement with earlier studies we found no initial (0-10 min) insulin secretion in response to glucose in islets prepared from mice up to 35 weeks of age. The islets of animals older than 40 weeks, however, were characterized by greater insulin content, and a restored typical biphasic insulin secretion profile. The results suggest that immediate glucose response is modified by environmental or other factors related to age.

Aging↗
PubMed1980

[Radioligand assay: methods and application. V. Mono-125I-insulin: preparation and immunological and biological characterization].

A reproducible method for preparation of 125I-monoiodoinsulin with fully biological activity was developed. Monoiodoinsulin has been prepared from a heterogeneous 125I-iodination mixture by anion exchange chromatography on DEAE-Sephadex A-25 without using any gradient elution technique. The specific radioactivity of 125I-monoiodoinsulin was calculated to 14.3 +/- 0.8 TBq/g, i.e. an iodine content of 1.04 +/- 0.06 atoms per molecule of insulin. Monoiodoinsulin was indistinguishable from native insulin with respect to binding to guinea pig anti-insulin serum, and to insulin receptors of isolated rat adipocytes. The biological potency (96.5 +/- 7.5 per cent of the immunoreactive insulin activity) determined by the conversion of [14C1]-D-glucose to 14CO2 in vitro by rat fat cells was not significantly different from that of native insulin.

Animals↗
PubMed1978

Effects of sulphydryl reagents on pancreatic glucagon secretion in vitro.

The effect of sulphydryl reagents on glucagon secretion of isolated Wistar rats islets was studied. Chloromercuribenzene-p-sulphonic acid (CMBS) is a strong stimulator of glucagon secretion, whereas 5,5'-dithiobis (2-nitrobenzoic acid) (DTNB) markedly inhibited the hormone release. The effect of CMBS could not be suppressed by 20 mM glucose, but in the presence of 1 mM 4-acetamido-4'-isothiocyano-stilbene-2,2'-disulphonic acid (SITS), and is independent of the glucagon content of islets. The results let us assume that sulphydryl-groups of pancreatic A-cells are involved in the regulation of glucagon secretion.

4-Chloromercuribenzenesulfonate↗
PubMed1978

[Insulin binding to isolated cells].

Using mono-125I-insulin the hormone receptor binding on cultivated rat hepatocytes cultivated rat fibroblasts and freshly isolated adipocytes of wistar rat and man were characterized. No specific insulin binding was obtained in the case of long time cultivated hepatocytes. The fibroblasts show a low specific insulin binding with an affinity constant of K = 0.75. 10(9)M-1 and a binding capacity of q = 4000 binding sites per cell, and also an insulin response measureable by the lactate production. In agreement with a strong stimulation effect of insulin on the conversion of glucose to CO2 und triglycerides the freshly isolated adipocytes bind insulin with high affinity and capacity in comparison with the fibroblasts. For the high affinity population of insulin receptors at the adipocytes of wistar rat we found K = 2.8 . 10(9) M-1 and q = 22000 binding sites per cell, whereas 20 per cent of saturation of the receptors cause 90 per cent of the maximal stimulation effect on the bio-conversion of glucose. This shift of the binding curve to higher concentrations may be important for the ability of insulin to regulate the carbohydrate metabolism.

Adipose Tissue↗
PubMedDate not supplied

Mumps infection and insulin-dependent diabetes mellitus (IDDM).

In order to select a population at risk for the development of diabetes for a prospective study of the relationship of islet cell antibodies (ICA), islet cell surface antibodies ( ICSA ), and glucose tolerance after mumps infection, we carried out a screening program for diabetes. A diabetic survey was conducted among 1581 children (less than 16 yr of age) with mumps infection 14 mo before the survey, using a brief questionnaire combined with urinary glucose analysis. Responses to the screening program were obtained from 68.4% (N = 1080) of the children. Out of a total of 1080 subjects, 1069 (99%) had no diabetes mellitus, diabetic symptoms, or glucosuria. A "positive urine glucose screen" was obtained in 11 subjects (1%) of the study group. These individuals all had a normal oral glucose tolerance test according to the new WHO definition. A group of 86 children was randomly selected from the total group of 1080 children for follow-up glucose tolerance, ICA, and ICSA . Irrespective of the negative urine glucose screen impaired glucose tolerance was diagnosed in 3.5% (N = 3) of the 86 children. The prevalence of ICA and ICSA was 78% and 36%, respectively. The simultaneous prevalence of ICA and ICSA was 33%. The pathogenetic role of mumps infection and ICA/ ICSA and their possible relationship to slow progressive beta cell destruction remain to be elucidated.

Animals↗